A system of gene rescue, where cytoplasmic petites are crossed to UV irradiated grande cells, will be employed to determine the presence of polypeptide structural genes on mtDNA in cytoplasmic petites of Saccharomyces cerevisiae. This technique will be used to attempt to map these genes by deletion mapping procedures. DNA-Cellulose chromatography will be used to compare the profile of yeast 0NA-binding proteins in respiratory competent cells and in cells whose mitochondrial function has been perturbed genetically or physiologically. Attempts will be made to detect putative regulatory species which function in mitochondrial biogenesis.